If it's likely to be always on the move, frequently carried around from place to place and therefore needs to be sturdy and dependable, I would use what most of the industry uses for their engineers and site technicians - a Panasonic Toughbook.
Not cheap, but you would need to replace a consumer laptop several times over a given period if used under the same conditions and in the same environments.
A laptop with matte finish screen to prevent sun glare, with an ssd drive, a dedicated graphics chip "switchable" if possible and finally an array of ports.
I personally use my msi gx60.